Hi guys

 

At the moment, if Wireshark comes across an unexpected data-link level
type in the global header when reading a PCAP file, it completely
rejects the file. This doesn't allow the user to apply any intelligence,
e.g. by manipulating the "wtap_encap" dissector table using Lua.

 

A quick hack prototype suggests that it is possible to read unknown or
mis-labelled data; the frame dissector just hands it off to the data
dissector. 

 

a) Would adding an option allowing unrecognised data to be read in from
a PCAP file cause any side-effects that I haven't spotted? The only
changes other than setting up the option would be in
libpcap.c:libpcap_open, so that it would continue processing an
unrecognised type.

 

b) What would the best way be of adding this option? My first thought
was to make it a preference, but the wiretap library has no dependencies
on the epan module where the preferences are. It looks like it would
take some careful wiring to add in the option without introducing a
dependency (which I think would break some of the apps). Setting up a
new (non-protocol) preference might also have to be duplicated across
tshark and wireshark, which is ugly.

 

Cheers

 

Doug

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Douglas Pratley
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